1. Field of the Invention
The present invention relates generally to a fuel injected multi-cylinder internal combustion engine, and more particularly to a single spot type fuel injected engine wherein the air-fuel distribution to the cylinders is improved by energizing the fuel injector twice per revolution of the crankshaft.
2. Description of the Prior Art
In prior art single spot injection arrangements fuel has been injected either once or three times per revolution of the engine crankshaft. However these methods have suffered from the drawbacks that the single injection fails to provide an adequate fuel distribution while in the case of three injections per revolution, the fuel distribution at low engine speeds is good, but as the engine speed is increased the frequency with which the injector must be energized exceeds the limit wherein the desired fuel injection and the actual injection fail to coincide, resulting in a marked deterioration in engine control. When the engine speed is 6000 RPM, the frequency of actuation of the injector is approximately 300 Hz (as compared with 100 Hz at lower engine speeds). At this speed, the correspondence between the pulse width and the amount of fuel injected in response to that particular pulse width loses its linearity.